The need to improve and simplify interactive computing svstems has led to the study of the human factors of these systems. Out of these studies and a general interest in ease of use has come a variety of guidelines and techniques for improving human-machine interfaces. Some of the most important. techniques allow a user to obtain assistance automatically while using a computer svstem. An introduction to the problems, methods, and results in human factors and user assistance for interactive computer systems are provided in this paper and this issue.

As interactive users find conventional methods of training and documentation inadequate, designers are providing systems with online reference information, descriptions of valid input, elaboration of error messages, and explanations of a system's behavior. This paper describes some existing commercial systems that offer online assistance and more experimental approaches by the research community. The following material was originally presented at the SIGSOC conference on Easier and More Productive Use of Computing Systems. An extended version will appear in a special issue of the IEEE Transactions on Systems, Man, and Cybernetics (Volume SMC-12, March/April, 1982), and is reprinted here with the permission of the IEEE.Online user assistance is now offered on commercial systems and is the subject of investigation in experimental settings. It is difficult to compare the advantages and limitations of different approaches because they vary along many dimensions and because there is no commonly accepted terminology. A grouping of these dimensions into major categories is a necessary first step towards more empirical evaluations. The major software-related features of online assistance appear to fall into four categories:• access method -- the way users can construct or enter requests for assistance;• data structure -- the manner in which different portions of assistance information are related to each other;• software architecture -- how assistance requests and their responses are communicated among a user, an operating system, application programs, and the assistance database; and• contextual knowledge -- how much information is retained about the assistance environment, including the user, the application, and the tasks being performed.